how to implent watermark into mp3?

[yasuo]

Hi there,

im looking for a way to implent watermarks into audio(mp3) files.

I thought of just generating a voice speaking some code and mix it into the audio file.
it shall not disturb the audio, so i thought about stretching and/or phase-shifting it to some frequency humans cannot hear.

Would that work and wich (commandline)tools can be used to do this scriptable?
i would prefer to run the script on a LAMP-Server...

Or maybe there is another way?

greetings :-)

[wonkey_monkey]

it shall not disturb the audio, so i thought about stretching and/or phase-shifting it to some frequency humans cannot hear.

Well, the whole idea behind mp3 is to remove things humans can't hear, so just that may not work so well. Data can be embedded in such a way that it will survive all but the harshest of re-encodings, but from what little I know of it, it's pretty complicated stuff.

[raffriff42]

You can manipulate the least-significant bits to insert a hidden watermark, but this is easily defeated by ANY audio processing. https://www.google.com/search?q=HIDING+TEXT+IN+AUDIO+USING+MULTIPLE+LSB+STEGANOGRAPHY

[LoRd_MuldeR]

If you want a "real" watermark, not just some additional "meta data" that is easily removed, then that's not trivial to do, indeed. You can't simply "mix" your watermark into the original signal. Instead, you have to manipulate certain "properties" of the audio signal, so that you will be able to distinguish "marked" from "unmarked" audio. And you need (at least) two distinct "marked" states, if you want to embed an actual (binary) message, instead of just being able to recognize whether a signal is "marked" or not. And, of course, this all needs to be done in a way that (A) doesn't impact audio quality too much, (B) survives the common attacks like MP3/AAC compression or analogue re-recording and (C) depends on a secret key.

There are commercial solutions available, but nothing Freeware or OpenSource that I'm aware of ;)